Amplifying system



Dec. 9, 1924. 1,518,625

w. c. WHITE AMPLIFYING SYSTEM Original Filed July 8. 191

I s I 9 a 7 I 1 20 Inventor: v

William C. White,

by ag His Att orney.

Patented Dec. 9, 1924. p V UNITED, STATES PATENT OFFICE.

WILLIAM 0. WHITE, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

AMPLIFYIN G SYSTEM.

Original application fliled July 8, 1919, Serial No. 309,306. Divided and this application filed November 15, 1923. Serial No. 674,990.

To all whom it may concern:

Be it known that I, WILLIAM C. WHITE, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Amplifying Systems, of which the following is a specification.

This application is a division of 'my former application, Serial No. 309,306, filed July 8, 1919.

My present invention relates to amplifying systems, and particularly to systems in which a 1plurality of-amplifiers are connected in paral el The object of my invention is to prevent in such a system the generation of oscillations. A more specific object of my invention is to prevent the generation of oscillations in an amplifying system in which electron discharge amplifiers are connected in parallel.

In the employment of electron dscharge amplifiers, having the usual grid or input circuit and late or output circuit, it has been found.t at there is a marked tendency toward the production of oscillations by reason of the natural coupling which exists between the input and output circuits. When it is desired to employ a plurality of these amplifiers in parallel this tendency is magnified because of the fact that the capacity coupling which exists between the circuits inside of the tubes and the capacity and magnetic coupling of the circuits outside the tubes becomes much greater than when a single amplifier "is employed. 1 have discovered that thistendenc may be entirely eliminated by including in the grid or input circuit of one or more of the amplifiers a small inductance.

The novel features which I believe to be characteristic-of my invention are set forth with particularity in the appended cla'ms, the invention itself howeveras to both its organization and method of operation will best be understood by reference to the. following description taken in connection with the accompanying drawing in which Figs. 1 and 2.indicate diagrammatically two circuit organizations whereby my invention may be carried into efiect.

The system indicated in Fig. 1 of the drawing comprises a plurality of electrondischarge amplifiers, 1, 2, 3, to 6, each having the usual cathode7, grid 8, and plate or anode 9. A source of current 10 supplies current to all of the cathodes in parallel for heating them to inoandescence to cause them to emit electrons. The grid or input circuits of all of these amplifiers which include the cathodes 7 and grids 8 are connected in parallel and a common port'on of these grid circuits includes the secondary 11 of a transformer by means of which thecurrents to be amplified are supplied to the system. In

plate circuits also includes the primary 16 of a.

a transformer 17, the secondary of which supplies amplified currents to any circuit desired and which may be connected to the conductors 18. There is present in the ampl fiers of the type here'involved a certain amount of capacity between the different electrodes. This capacity serves as a coupling between the grid and plate circuits, while the capacity between the elements of a single device is ordinarily small, where a plurality of devices are employed as in the present arrangement the capacity coupling between. the circuits becomes appreciable. There is also present in the c'rcuits a certain amount of inductance due to the leads and this combination produces a tendency in the system to the generation of oscillations the frequency of which will be determined by the capacity and inductance of the system. These oscillations will ordinarily be of comparatively high frequency and this tendency is very troublesome. In some cases when the system starts to oscillate the amplifiers will no longer operate, fuses inserted at various places for the protection of the system will be blown, and the source of supply current may be broken down. I have found that this tendency for the production of oscillations may in some cases be entirely eliminated by the insertion of an inductance 19 in the grid circuit of one of the amplifiers. This inductance may be comparatively small, a few microhenries being suflicient for the purpose. It is important for the. suppression of oscillations that this indudzance be placed in that portion of the grid circuit of the amplifier to which it is connected, which is close to the grid of that particular amplifier, that is, the beneficial results will not be obtainedwhen' the inductance. is placed in the circuit in sucha Way that it is common to all of the grid circuits." The reason why the use of this in.- ductance produces the results set forth is 'not entirely clear. It seems probable, however, that its effect is to shift thephase of the current through the coupling capacity so that is no longer in the proper phase to cause the generation of oscillations.

While, as above stated, the use of an inductance in. only one of the grid circuits may be suffici'ent for the desired purpose, I have'indicated in Fig. 1 the amplifiers as being divided into three groups of two each, these groups being separated so that the leads joining them are of considerable length. In this case the use of a single inductance may not be suflicient and I have therefore indicated inductances 19 in the grid circuit of one amplifier of each grou In Fig. 2 I have shown only three amplifiers, 20, 21 and 22, and have shown in-- ductances 19 in the grid circuit of each one of these amplifiers. This may be desirable where the length of the leads between the individual amplifiers are of such length that by'reason of their inductances the usecof a small inductance in the grid circuit of one of the amplifiers does not entirely accomplish the desired purpose.

While I have indicated and described only two embodiments of my invention it will be apparent to one skilled in thea'rt that my discharge devices having their correspond-"' ing electrode circuits connected in parallel,

a choking inductance in anumber of the corresponding electrode circuits.

2. In a system comprising a number of discharge devices each having plate, grid" and filament electrode circuits, their corre- Y sponding circuits being in parallel, separate choking inductances individual to said corresponding electrode circuits respectively.

3. In a system comprising-a number of discharge devices having their corresponding electrode circuits connected in parallel, choking inductances in a number of the corresponding grid circuits.

' 4. In a system comprising a number of discharge devices each having plate, grid and filament electrode circuits, their corresponding circuits being in parallel, separate choking inductances individual to said corresponding grid circuits respectively.

5.Ina system comprising a number of discharge devices having plate, grid and filament electrode circuits, their corresponding. circuits being in parallel, separate choking inductances individual to each of the corresponding d circuits.

In witness w ereof, I have hereunto set my hand this 12th day of November 1923.

WILLIAM C. WHITE. 

